Design of Frustrated Lewis Pairs by Functionalizing N-Doped Graphene Edge with Tunable Activity for H2 Dissociation

Abstract

While the frustrated Lewis pair (FLP) concept has been successfully extended to heterogeneous catalysis, the underlying factors governing the catalytic performances of FLPs and designing strategies remain elusive. Herein, a theoretical study is performed to design metal-free heterogeneous FLPs with tunable activity for hydrogen dissociation. The designed FLPs constructed by functionalizing the N-doped zigzag graphene edge with eight functional groups −BX2 (X = F, Cl, Br, H, CH3, CF3, CN, NO2) can readily heterolytically dissociate H2 (H2 → Hδ− + Hδ+) with reaction barriers varying from 0.15 to 0.70 eV, showing their comparable activity to homogeneous FLPs. More importantly, FLP acidities of designed FLPs are linearly correlated with the reaction energies of H2 dissociation, suggesting the significant role of FLP acidity in determining their catalytic activity. Further calculations show that the reaction barriers of hydrogenation of CO2 also linearly correlate with the reaction energies of H2 dissociation and accordingly are governed by FLP acidity. Overall, this study provides a route for designing metal-free heterogeneous FLPs on graphene materials and discloses a close relationship between the composition (N···BX2), the electronic structure (FLP acidity), and the functionality (catalytic ability) of the FLPs.